Unless specifically indicated otherwise, the materials described in this section are not prior art to the claims in this application, and are not admitted to be prior art by inclusion in this section.
The material in this patent document is subject to copyright protection under the copyright laws of the United States and other countries. The copyright owner grants a limited license to any member of the public to reproduce the patent document as it appears in official governmental records. All other copyrights rights are reserved.
Persons, such as would-be thieves or trespassers, often employ a tool called a “jimmy” to open a locked door. Typically, a thin flexible tool, such as a credit card, is used as a jimmy. The jimmy is inserted into the gap between a closed and locked door and the door jamb and pressed against the latch bolt, thereby causing the latch bolt to withdraw from the door jamb and the door to be unlocked.
A number of devices have been disclosed in the conventional art to address the problem of the jimmying of door locks (also referred to as credit card entry) by a person using a jimmy, such as a credit card or a similar tool. Each of these conventional art devices suffers limitations and disadvantages.
One approach to address the problem of credit card entry is to design an entire jimmy-proof door lock mechanism. U.S. Pat. No. 4,031,725 to Reid is representative of this general approach. Reid discloses a door lock that utilizes a standard keyed lock assembly in combination with a latch fitted in sliding relationship with a channel shaped dead bolt member such that, when the dead bolt is extended over the latch into the door jamb opening, the door is secured against unauthorized entry commonly accomplished by the use of credit cards and the like. The invention of Reid further comprises linkage and latch assemblies for manipulating the late and dead bolt sleeve. Practical disadvantages and limitations of such inventions include that they are not designed to be readily adapted to, or used in combination with, existing conventional door locks and door latch devices. Therefore, use of such inventions requires the considerable expense of purchasing an entire door lock assembly, and the considerable cost, inconvenience, and mechanical challenge of replacing the existing door lock with the jimmy-proof door lock. Such inventions are not suitable after-market solutions to the problem of credit card entry. In addition, such inventions are complex and expensive to manufacture.
Another approach to solving the problem of credit card entry is to provide a physical barrier to the jimmy. An example of this approach is U.S. Pat. No. 3,936,085 to Long. Long discloses a lock protector consisting of a strong metal door plate of U-form adapted to bridge the free edge of a door at the lock and aperture to pass the lock bolt, and a chain plate adapted to be strongly affixed to the door frame, the safety chain being permanently affixed to the door plate and detachably connected to the chain plate. Additionally, the chain plate has a fixed metal flange, formed integrally to the strong metal chain plate, intended to defeat credit card entry. Practical disadvantages and limitations of the invention of Long dictate that the device is not a practical after-market solution to the problem of credit card entry. The device of Long is mechanically complex and accordingly expensive. Further, the device of Long may not be installed on an existing door/door jamb assembly without inconvenient and challenging modification of the door/door jamb assembly. In addition, the device of Long is fully accessible to a potential intruder and, therefore, may be defeated by such potential intruder with a tool to pry the protective flange. Finally, the device of Long does not accommodate various door-to-door jamb gap tolerances.
What is needed is a door security device that: defeats jimmying (or credit card entry); is compatible with the door security after-market; is adapted for use on existing door-door jamb installations; is simply installed without modification of the existing door-door jamb installation; accommodates a variety of door-to-door jamb gaps; prevents a jimmy from reaching the door latch bolt from above or below the latch bolt; cannot be accessed and defeated by a potential intruder; and is low cost.